Faik Bakir, the director of the Baghdad morgue, has fled Iraq in fear of his life after reporting that more than 7,000 people have been killed by death squads in recent months, the outgoing head of the UN human rights office in Iraq has disclosed.

"The vast majority of bodies showed signs of summary execution - many with their hands tied behind their back. Some showed evidence of torture, with arms and leg joints broken by electric drills," said John Pace, the Maltese UN official. The killings had been happening long before the bloodshed after last week's bombing of the Shia shrine in Samarra.

Mr Pace, whose contract in Iraq ended last month, said many killings were carried out by Shia militias linked to the interior ministry run by Bayan Jabr, a leading figure in the Supreme Council for the Islamic Revolution in Iraq (Sciri).

Mr Pace said records, supported by photographs, came from Baghdad's forensic institute, which passed them to the UN. The Baghdad morgue has been receiving 700 or more bodies a month. The figures peaked at 1,100 last July - many showing signs of torture.

Reports of government-sponsored death squads have sparked fear among many prominent Iraqis, prompting a rise in the number leaving the country. Mr Pace said the morgue's director had received death threats after he reported the murders. "He's out of the country now," said Mr Pace, adding that the attribution of the killings to government-linked militias did not come from Dr Bakir.

"There are other sources for that. Some militias are integrated with the police and wear police uniforms," he said. "The Badr brigade [Sciri's armed wing] are in the police and are mainly the ones doing the killing. They're the most notorious."

Some Iraqis accuse the Mahdi army militia, linked to the radical cleric Moqtada al-Sadr, of seizing and killing people. But Mr Pace said: "I'm not as sure of the Mahdi army as I am of the others."